David Delaere

Influence of building block aromaticity in the determination of electronic properties of five-membered heterocyclic oligomers

This theoretical study investigates the influence of the building block aromaticity in the determination of electronic properties of five-membered heterocyclic oligomers. More specifically, we considered some fundamental energetic and electronic properties such as energy gaps, vertical ionization energies and static polarizability tensors of oligomers (up to octamers) built from five-membered heterocycles such as cyclopentadiene, pyrrole, furan, silole, (planar) phosphole and thiophene. Our computations are based on ab initio quantum mechanical methods including (time-dependent) density functional theory. We have chosen NICS as a quantitative criterion for measuring aromaticity and making a distinction between aromatic and non-aromatic building blocks.

Structure-property relationships in phosphole oligomers: a theoretical insight

Abstract The influence of cyclic π-conjugation and interannular rotation on the vertical ionization energies and energy gaps of phosphole oligomers has theoretically been investigated which provided some useful structure–property relationships. While vertical ionization energies were obtained from negative HOMO-energies using the Hartree–Fock method, energy gaps were calculated using a DFT/hybrid method (B3LYP). Combination of geometric (JULG and d Cα ) and magnetic (NICS) criteria gives a qualitative indication about the competition between the cyclic- and the carbon backbone π-conjugation. Results of this preliminary theoretical study suggest that phosphole oligomers have interesting tunable electronic properties.

A density functional study of the ground state electronic structure of phosphorus-porphyrins

Geometries of the ground state and energies of the lower-lying excited singlet states of phosphorus-containing porphyrins were computed using DFT and TD-DFT methods, respectively, and compared with those of N-porphyrins. The P-analogues of porphyrins were obtained by successively replacing a NH- by a PH-unit or a N- by a P-atom within N-porphyrins. The goal of this theoretical study is to elucidate the modifications in the electronic structure and to predict the shift of Q- and B-bands in the UV–VIS absorption spectrum of porphyrins following substitution of nitrogen by phosphorus atoms. The interesting features could be of help in the identification of the P-substituted porphyrins that are not known yet. 2003 Elsevier B.V. All rights reserved.

A theoretical study on the molecular and electronic structure of heteroaromatic bowl-shaped molecules

Abstract Geometries, inversion barriers, local aromaticities and vertical excitation energies of four heteroaromatic coronenes including (triphenylenotri)-pyrrole, (-)-furan, (-)-phosphole and (-)-thiophene were computed using MO and DFT methods, and compared with those of coronene and corannulene. The barriers to bowl-to-bowl inversion amount to 297, 183 and 8 kJ/mol for O-, N- and S-forms, respectively, thus the recently synthetized thiophene derivative is a floppy bowl-shaped species. The P-derivative exhibits an almost planar form. NICS values point out that the bowl-shaped molecules have similar local aromaticity in the six-membered rings but differ in those of the five membered rings. The excitation energies were evaluated using the DFT-RPA method.